Sulfur oxides and nitrogen oxides gas treating process

• US 4,504,450 A
• Filed: 12/20/1983
• Issued: 03/12/1985
• Est. Priority Date: 12/20/1982
• Status: Expired due to Fees

• Current Assignee: UOP Des Plaines IL A NY General Partnership
• Original Assignee: UOP Llc (Honeywell International Inc.)
• Inventors: Forbes, James T.
• Primary Examiner(s): HELLER, GREGORY
• Application Number:
  US06/451,513
• Time in Patent Office: 448 Days
• Field of Search: 55/73, 55/74, 55/77, 423/244 R, 423/244 A, 423/239, 423/239 A
• US Class Current: 423/239.1
• CPC Class Codes: B01D 53/60 Simultaneously removing sulfur oxides and nitrogen oxides
• CPC Class Codes: F23J 15/006 Layout of treatment plant
• CPC Class Codes: F23J 15/08 of heaters
• CPC Class Codes: F23J 2215/20 Sulfur; Compounds thereof
• CPC Class Codes: F23J 2219/10 Catalytic reduction devices
• CPC Class Codes: Y02A 50/20 Air quality improvement or preservation, e.g. vehicle emission control or emission reduction by using catalytic converters

Abstract

A process is disclosed for treating particle-containing gas streams by removing particles and gaseous atmospheric pollutants. Parallel passage contactors are utilized to remove the gaseous pollutants. The minimum required gas flow rate for effective operation of these contactors is maintained by recycling a variable amount of low temperature gas which has been passed through a particle removal zone. The recycled gas is reheated by heat exchange against a portion of the treated gas.

Claims

1. A gas treating process for reducing the concentration of sulfur oxides and nitrogen oxides which comprises the steps of:

(a) admixing a hereinafter characterized recycle gas stream into a feed gas stream containing sulfur oxides and nitrogen oxides and passing the resultant admixture through a treating zone in which the concentration of the sulfur oxides and nitrogen oxides is reduced to a level below that in the feed gas stream to form a treated gas stream;

(b) cooling a first portion of the treated gas stream in a first heat exchange means used to heat air fed to the source of the feed gas stream;

(c) cooling a second portion of the treated gas stream in a second heat exchange means used to heat said recycle gas stream; and

,

(d) discharging the first portion of the treated gas stream from the process and recycling the second portion of the treated gas stream as said recycle gas stream, which is heated and then admixed with the feed gas stream.

2. The process of claim 1 further characterized in that nitrogen oxides are catalytically reduced to nitrogen within the treating zone.

3. The process of claim 1 further characterized in that the recycle stream is further heated by combustion after being heated by heat exchange against the second portion of the treated gas stream.

4. A gas treating process for reducing the concentration of sulfur oxides and nitrogen oxides which comprises the steps of:

(a) admixing a hereinafter characterized recycle gas stream into a particle-containing feed gas stream containing sulfur oxides and nitrogen oxides and passing the resultant admixture through a treating zone in which the concentration of the sulfur oxides and nitrogen oxides is reduced to a level below that in the feed gas stream to form a treated gas stream;

(b) cooling a first portion of the treated gas stream in a first heat exchange means used to heat air fed to the source of the feed gas stream;

(c) cooling a second portion of the treated gas stream in a second heat exchange means used to heat said recycle gas stream;

(d) passing the first and the second portions of the treated gas stream through a particle removal zone to form a processed gas stream; and

(e) discharging a first portion of the processed gas stream from the process and recycling a second portion of the processed gas stream as said recycle gas stream, which is heated and then admixed with the feed gas stream.

5. The process of claim 4 further characterized in that nitrogen oxides are catalytically reduced to nitrogen within the treating zone.

6. The process of claim 4 further characterized in that the recycle stream is further heated by combustion after being heated by heat exchange against the second portion of the treated gas stream.

7. The process of claim 4 further characterized in that the treating zone comprises parallel passage contactors.

8. The process of claim 7 further characterized in that the parallel passage contactors contain acceptor particles which comprises copper.

9. The process of claim 5 further characterized in that the treating zone comprises parallel passage contactors.

10. The process of claim 9 further characterized in that the parallel passage contactors contain catalyst particles which comprise copper.

11. The process of claim 9 further characterized in that the parallel passage contactors contain catalyst particles which comprise either vanadium or tungsten or both.

12. A gas treating process for reducing the concentration of sulfur and nitrogen oxides which comprises the steps of:

(a) admixing a hereinafter characterized recycle gas stream into a particle-containing flue gas stream containing sulfur oxides and nitrogen oxides and passing the resultant gas admixture into a treating zone operated at treating conditions including an elevated temperature and in which the gas admixture is passed through parallel passage contactors containing gas treating particles to form a treated gas stream having a reduced concentration of sulfur oxides and nitrogen oxides;

(b) cooling a first portion of the treated gas stream by heat exchange against an air stream;

(c) cooling a second portion of the treated gas stream by heat exchange against said recycle stream;

(d) removing entrained particles from the first and the second portions of the treated gas stream in a particle removal zone to form a processed gas stream; and

(e) dividing the processed gas stream into a first portion which is withdrawn from the process and a second portion which is recycled as said recycle stream.

13. The process of claim 12 further characterized in that the flow rate of the recycle gas stream is varied as required to maintain a predetermined minimum total gas flow through the treating zone.

14. The process of claim 13 further characterized in that the flow rate of the second portion of the treated gas stream is varied as required to compensate for changes in the flow rate of the recycle stream.

15. The process of claim 12 further characterized in that a gaseous reductant is added to reduce the nitrogen oxides and is consumed in the reduction of nitrogen oxides is also passed into the treating zone.

16. The process of claim 15 further characterized in that the gas treating particles comprise vanadium.

17. The process of claim 15 further characterized in that the gas treating particles comprise tungsten.

18. The process of claim 15 further characterized in that the gas treating particles comprise copper.